Make the sauce preferably in a food processor or a blender that can be “pulsed.” Process the parsley, garlic and onion until medium fine. Add tomatoes and seasonings and process just to break up the tomatoes, but leave them slightly chunky. In a 12-inch skillet, heat the oil over medium-high heat. Brown the chicken and drain off excess fat. Pour the sauce over the chicken in pan. Tilt cover just slightly and simmer for 45 minutes or until chicken tests tender. Add the mushrooms the last 15 minutes, stirring with the sauce occasionally. You can substitute canned diced tomatoes for the whole ones. Serves 4.